1. Field of the Invention
The present invention relates to capsules for use in heavy duty liquid detergent compositions which capsules comprise
(1) a component subject to degradation; and
(2) a novel composite polymer comprising hydrophobic particles and hydrophilic polymers attached thereto wherein the sensitive component is entrapped within the composite polymer.
2. Prior Art
It is well known in the art that heavy duty liquid detergents provide a hostile environment for desirable ingredients such as, for example, bleaches, enzymes and perfumes. It is therefore often desirable to protect a sensitive component such as an enzyme from the composition during storage yet ensure its release in a controlled and reproducible manner when the liquid is used by consumers. In this manner, components which are sensitive to the ingredients found in the compositions (e.g., enzymes in detergent compositions, particularly concentrated detergent compositions, are denatured by surfactants in the detergent composition) can be encapsulated and protected until they are ready for release; or other components which are simply more desirably released later in the wash (e.g., perfumes or anti-foams) can be controllably released, for example, by dilution of a concentrated liquid.
In particular, it is desirable to encapsulate one or more enzymes since enzymes are highly efficient laundry washing ingredients used to promote removal of soils and stains during the cleaning process.
European Patent Application No. 266,796 (assigned to Showa Denko), for example, teaches water-soluble microcapsules comprising an enzyme, preferably dissolved or dispersed in a water containing polyhydroxy compound, and coated with a water soluble polyvinyl alcohol (PVA) or partially hydrolyzed polyvinyl alcohol as the coating material. There is no teaching or suggestion of composite polymer comprising a network formed by hydrophobic particles to which are chemically or physically attached hydrophilic polymers and in which system or network enzyme or other sensitive component is entrapped. In addition, the PVA used in the Showa Denko reference, in contrast to the PVA which could be used as a hydrophilic component of the subject invention, has an average degree of polymerization in the range of 200-3000 and a percent hydrolysis not less than 90%, preferably not less than 95%. It is said that if the percent hydrolysis of PVA is lower than 90%, the microcapsule is not stable and will dissolve during storage in a water-containing liquid detergent. This is probably not surprising in that there is nothing to stabilize the capsule other than a cross-linking agent, i.e., there is no teaching or suggestion of hydrophobic core particles comprising an ethylenically unsaturated group to which the hydrophilic polymers can affix, chemically or physically, to form an entrapping network.
That is, the encapsulating polymer of this reference comprises only the use of a water soluble polymer (i.e., PVA) rather than an entrapping polymer which is a composite emulsion copolymer comprising both water-soluble (i.e., hydrophilic attaching polymer) and water insoluble (i.e., hydrophobic particles to which hydrophilic polymers attach) components or domains. The use of a totally water soluble polymer does not provide optimal resistance to water such polymers are also more difficult to process than the composite polymers of this invention. Finally, at the levels of hydrolysis for PVA taught in this reference (i.e. greater than 90%, preferably greater than 95%), it is difficult to dissolve the capsule or polymer at ambient temperatures and the protected component is only partly released upon dilution. Moreover, the reference does not allow the option of using less hydrolyzed PVA because, although the less hydrolyzed PVA will dissolve more readily when diluted, such a PVA is too water sensitive and would fail to protect the component during storage.
U.S. Pat. No. 4,906,396 to Falholt et al. teaches an enzyme dispersed in a hydrophobic substance. Again, there is no teaching or suggestion of a polymer which is a composite emulsion copolymer comprising both water soluble and water insoluble components.
EP 1,390,503 (assigned to Unilever) teaches a polymer which dissolves when the ionic strength of the liquid decreases upon dilution. Further, there is no teaching of a polymer system comprising a composite emulsion polymer which in turn comprises a hydrophilic portion (i.e., hydrophilic polymer or polymers) chemically and/or physically attached to a hydrophobic core portion (i.e., hydrophobic particles) to form an entrapping emulsion polymer in which the enzyme component is trapped.
Takizawa et al. (U.S. Pat. Nos. 4,777,089 & 4,908,233) teach the use of a microcapsule which comprises a "core" material (i.e., the protected material is the core) coated with a single water soluble polymer (which polymer undergoes phase separation by the action of an electrolyte in the compositions). Again, there is no teaching or suggestion of a composite emulsion polymer comprising a hydrophilic portion chemically or physically attached to hydrophobic core particles and used to entrap sensitive materials subject to degradation. Such a composite polymer having both a hydrophilic and hydrophobic portion offers significant advantages over the solely water-soluble encapsulating polymers of the reference in that it entraps the component and slows migration of harsh components from outside the capsule to the sensitive component as well as slows migration of the sensitive component to water and harsh components outside the capsule.
U.S. Pat. No. 4,842,761 to Rutherford teaches compositions and methods for controlled release of fragrance-bearing substances (perfumes) wherein the compositions comprise a water-soluble and a water-insoluble (both normally solid) polymer and a perfume composition, a portion of the perfume composition being incorporated in the water-soluble polymer and a portion incorporated in the water-insoluble polymer. The two polymers are physically associated with each other in such a manner that one is in the form of discrete entities in a matrix of the other. The particles of this reference have a particle size of between 100-3000 microns in contrast to the capsules of the invention which have a particle size of under 100 microns. In addition, the capsules are formed by intermixing water soluble and water insoluble polymer under high shear resulting in a different capsule system than the emulsion polymer capsule of the subject invention.
Applicants co-pending U.S. Ser. No. 07/766,477 now U.S. Pat No. 5,296,977 teaches a water soluble polymer used to encapsulate particles made of an emulsifiable mixture of a fragrance and a wax. The waxes used are hydrocarbons such as paraffin wax and microcrystalline wax. These waxes differ from the core hydrophobic particles of the invention. Moreover, the core is not simply a wax material enveloping the perfume but an intimate mixture of the wax and perfume which differs completely from the core particles of the subject invention which may stand alone. In fact, the enzymes of the subject invention are not inside the hydrophobic core particles at all. Finally, the encapsulated material of the reference is released by heat trigger whereas the material of the invention is dilution triggered.
U.S. Pat. No. 4,115,474 to Vassiliades discloses a hydroxy containing polymer shell be grafted onto a water insoluble core. They hydroxy shell is cross-linked with a formaldehyde condensation product and will chloroform not release upon dilution by water. Moreover, the reference has not even refer to entrapped sensitive materials which can be released. Indeed, the capsule is intended to be a load bearing capsule which is not even subject to pressure release.
None of these patents teach capsules comprising the specific composite emulsion polymers of the invention which are intended for dilution release of entrapped sensitive materials.
Thus, there is a need in the art for capsules for use in heavy duty liquid compositions wherein said capsules comprise novel composite polymers which can both stabilize components subject to degradative attack and yet readily break down to release the component in use (e.g., in diluted aqueous medium, especially at ambient temperatures).
Accordingly, it is an object of this invention to provide such a novel composite polymer that can stabilize and isolate sensitive ingredients in heavy duty liquid compositions while simultaneously being able to deliver the ingredients in a controlled and reproducible manner when the composition is diluted with water during use.